Evidence of a Cubic Iron Sub-lattice in T-CuFeO Demonstrated by X-ray Absorption Fine Structure

Copper ferrite, belonging to the wide and technologically relevant class of spinel ferrites, was grown in the form of t-CuFeO nanocrystals within a porous matrix of silica in the form of either an aerogel or a xerogel, and compared to a bulk sample. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed the presence of two different sub-lattices within the crystal structure of t-CuFeO, one tetragonal and one cubic, defined by the Cu and Fe ions respectively. Our investigation provides evidence that the Jahn-Teller distortion, which occurs on the Cu ions located in octahedral sites, does not affect the coordination geometry of the Fe ions, regardless of their location in octahedral or tetrahedral sites.